Apparatus, System, and Method For Signaling a Quantity of Antenna Ports in a Wireless Communication System

ABSTRACT

A quantity of antenna ports of a transmitting apparatus is signalled in a wireless communication system. The quantity of antenna ports of the transmitting apparatus is encoded into a first type information and a second type information. The first type information is transmitted on a physical broadcast channel (PBCH) and the second type information is transmitted on a physical downlink shared channel (PDSCH). The PDSCH is transmitted on at least one antenna port indicated by the first type information.

This is a continuation of U.S. patent application Ser. No. 14/511,754,filed on Oct. 10, 2014, which is a continuation of U.S. patentapplication Ser. No. 13/165,544, filed on Jun. 21, 2011 (now U.S. Pat.No. 8,885,529), which is a continuation of International Application No.PCT/CN2009/072516, filed on Jun. 29, 2009, which claims priority toInternational Application No. PCT/CN2008/073631, filed on Dec. 22, 2008.The aforementioned patent applications are hereby incorporated byreference in their entireties.

TECHNICAL FIELD

The present disclosure relates to a method in a wireless communicationsystem for signaling number of antenna ports. Furthermore, thedisclosure also relates to a transmit node and a receive node, andmethods thereof.

BACKGROUND

In a wireless cellular communication system, one or multiple Downlink(DL) Common Reference Signals (CRSs) may be used for channelmeasurements, or for coherent demodulation and channel measurements, fora mobile terminal in a given cell. A mobile terminal is also denoted asa User Equipment (UE) in some wireless communication systems. Each CRSdefines a so-called antenna port in a given cell and a common way toimplement antenna ports is to associate an antenna port with a physicaltransmit antenna.

The Reference Signals (RSs) of different antenna ports should beorthogonal to each other to allow interference-free identification ofcorresponding propagation channel coefficients, i.e. the propagationchannel from each transmit antenna to each receive antenna. The RSs areusually cell-specific to minimize interference between RSs in differentcells. Without loss of generality, antenna ports are defined by CRS orcell-specific CRS throughout this document. Cell specific CRS impliesthat they are used by multiple UEs in a cell to measure the channel fromeach antenna port. Antenna ports may also be user specific, which meansthat they are used for measurements and/or demodulation by a specificsingle UE.

The CRSs are transmitted on exclusively reserved resources of a cell,such as time and frequency Resource Elements (RE), codes, etc. Data isnot transmitted on these reserved resources to avoid interference withRSs, which would hamper the estimation of the channel propagationcoefficients from that antenna port.

In order to be able to use DL CRSs properly and to perform standardcommunication with a base station, such as a eNB, the number of antennaports used for DL channel measurements and/or DL transmission is veryimportant information that a UE needs to know. After a UE obtaininformation about the number of antenna ports used in a cell, the UEwill know which transmission mode is used for each physical channel, andwhich resources that are used for data transmission and which that areused for DL CRS. This is important information to avoid that receiveddata is punctured by CRSs, since if a UE is not aware of all CRSs inradio resources, it will assume reception of data on those resourceswhere there actually is a CRS transmission, and this will degrade theperformance of data reception due to the interference from the CRSs.

Furthermore, knowing the number of CRSs is also important to measuremultiple channels using CRSs and to detect physical channels, etc. Inthe Long Term Evolution (LTE) Release-8 (Rel-8) standard, theinformation about number of antenna ports is embedded in the signaltransmitted on a Physical Broadcast Channel (PBCH). After successfulcell search procedure, the UE will obtain time and frequencysynchronization with a cell, as well as the cell Identity (ID) of thecell; and then the UE begins to detect the PBCH to obtain cell-specificinformation and the number of antenna ports.

In the LTE Rel-8 standard, three types of cell-specific CRS s aresupported defining: one, two and four antenna ports (3GPP TS 36.211v8.4.0). The number of antenna ports in a cell decides the maximumnumber of Multiple Input Multiple Output (MIMO) transmission layerssupported by a eNB in the cell. For instance, if there are four antennaports in a cell, up to four MIMO layers transmission can be supported bythe eNB. The information about the number of antenna ports is embeddedinto the signal transmitted on the PBCH by using different CyclicRedundancy Check (CRC) masks to indicate the number of antenna ports. Asa UE has no prior information about the number of used antenna ports ina cell, i.e. the used CRC mask of the transport block of the PBCH, theUE has to make blind detection of that information, which means that ithas to check all possible CRC masks and select the mask that is the mostprobable conditioned on the received PBCH signal.

The operation of embedding information about the number of antenna portsinto PBCH at transmitter and the corresponding blind detection of PBCHat receiver for a LTE Rel-8 system will be described in the following.

Firstly, at the transmitter, the entire transport block bits of PBCH a₀,a₁, . . . a_(A-1) is used to calculate the CRC parity bits p₀, p₁, . . .p_(L-1) where A is the size of the transport block (i.e. the number ofinformation bits) and L is the number of CRC parity bits which is set to16 in the LTE Rel-8 standard. Secondly, according to the antenna portconfiguration of the cell, the CRC parity bits are scrambled by asequence having length 16, x₀ ^(n), x₁ ^(n), . . . x₁₅ ^(n)corresponding to a number of antenna ports n, where n=1, 2 or 4. Afterscrambling, the masked CRC parity bits will be c₀, c₁, . . . c₁₅, wherec_(i)=(p_(i)+x_(i) ^(n))mod 2, i=0, 1, . . . , 15. The mapping relationbetween the three scrambling sequences and the number of antenna portsaccording to the LTE standard is shown in Table 1 below.

TABLE 1 CRC mask sequences for PBCH in LTE Rel-8 Number of antenna portsCRC mask sequences 1 <0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0> 2<1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1> 4 <0, 1, 0, 1, 0, 1, 0,1, 0, 1, 0, 1, 0, 1, 0, 1>

Then, the masked CRC parity bits are attached to the tail of thetransport block bits of the PBCH to obtain the information bits to betransmitted as a₀, a₁, . . . a_(A-1), c₀, c₁, . . . , c₁₅.

Finally, a set of operations including channel coding, rate matching,modulation and resources mapping are performed on the information bitsa₀, a₁, . . . a_(A-1), c₀, c₁, . . . , c₁₅.

In the case of one antenna port, the modulation symbols are directlymapped to the reserved resources on antenna port 0; in the case of twoantenna ports, a transmit diversity scheme known as Space FrequencyBlock Coding (SFBC) is performed on the modulation symbols, and theoutput of the SFBC is mapped to the reserved resources on antenna port 0and 1, respectively; in the case of four antenna ports, SFBC combinedwith Frequency Switching Transmit Diversity (FSTD) is performed on themodulation symbols, and the output of SFBC+FSTD is mapped to thereserved resources on antenna port 0, 1, 2 and 3, respectively. Itshould be observed from the above description that the information aboutthe number of antenna ports is implicitly embedded into the PBCH.

At the receiver, the corresponding inverse operations to find the numberof antenna ports are done by a UE who is accessing to the cell. As theUE knows that there are three hypothesises possible regarding the numberof antenna ports (i.e. one, two or four antenna ports) the UE performsblind detection of the PBCH, which is illustrated in FIG. 1. In theprocedure of blind detection, SFBC or SFBC+FSTD decoding, demodulation,channel decoding and CRC detection are all standard operations, so thedetails of them will not be further described, but the operation ofremoving the CRC mask will be explained in the following disclosure.

Assuming that the output of channel decoding is â₀, â₁, . . . â_(A-1),ĉ₀, ĉ₁, . . . , ĉ₁₅, where the last 16 bits of information ĉ₀, ĉ₁, . . ., ĉ₁₅ are the CRC parity bits scrambled with a CRC mask corresponding toinformation about the number of antenna ports, as mentioned above. Whenblind detection of the PBCH is performed, the CRC parity bits arede-scrambled with an assumed CRC mask (i.e. removing the CRC mask) inthe following way:

{tilde over (c)} _(i)=(ĉ _(i) +x _(i) ^(n))mod 2 where i=0, 1, . . . ,15;

-   -   n is the number of antenna ports,    -   x_(i) ^(n) is the defined CRC mask corresponding to n antenna        ports

If the assumed CRC mask is the same as the actual CRC mask used attransmitter, the above operation will completely remove the CRC maskembedded into CRC parity bits, and the probability of correct detectionis increased.

As mentioned, in the LTE Rel-8 system up to four antenna ports can besupported on the DL. The LTE-Advanced (LTE-A) system of Release 10(Rel-10) and beyond are supposed to be an extension of LTE system inwhich up to eight layers transmission (possibly even more layers forreleases beyond Rel-10) will be supported to further increase systemperformance, such as peak data rate, cell average spectrum efficiency,etc (3GPP TR 36.814 v1.0.0). In order to support up to eight layerstransmission more antenna ports than the antenna ports supported in LTERel-8 must be defined in a LTE-A communication system.

In addition, to fulfil LTE-A backwards compatibility requirement, itshould still be possible for a LTE-A cell to also serve LTE UEs. Inorder to enable LTE UEs to operate in a LTE-A system, the antenna portsdefined in LTE should also be supported in a LTE-A system, i.e. n numberof LTE CRSs should also exist in a LTE-A system, where n=1, 2 or 4; andLTE UEs use LTE CRSs for coherent demodulation and channel measurementas in the LTE system, while LTE-A UEs may also use these LTE CRS fordemodulation of the control channels, such as PBCH and Physical DownlinkControl Channel (PDCCH).

Hence, in a LTE-A system there will be a number of LTE antenna portsused for transmitting LTE data/control and/or LTE-A control information;in addition, it is also possible to define a number of additionalantenna ports used only for supporting LTE-A data transmission. For allantenna ports in a LTE-A system, the new defined additional antennaports are denoted as LTE-A antenna ports, and the number of LTE-Aantenna ports could be zero. Therefore, a communication system which canserve both LTE UEs and LTE-A UEs is needed. Also, since the number ofLTE and LTE-A antenna ports may be different in a LTE-A cell, a questionis how to signal the existence of LTE-A antenna ports to LTE-A UEs inway that is transparent to the reception of the number of LTE antennaports.

It is thus clear that a LTE-A eNB may need to enable additional CRSs(antenna ports) for measurements and/or demodulation compared to theantenna ports defined by LTE CRSs (i.e. n=1, 2 or 4). Up to eightadditional antenna ports (CRSs) may be needed for LTE-A UEs in Rel-10.These additional CRSs are denoted Channel State Information-RSs(CSI-RSs). It is thus another question how to signal the number of LTE-Aantenna ports or the number of CSI-RS to LTE-A UEs in way that istransparent to LTE UEs.

Therefore, a signalling method which is backwards compatible to enableLTE UEs to obtain the number of LTE antenna ports, while the signallingof LTE-A antenna ports should be transparent to LTE UEs is needed in theart.

SUMMARY

An object of the present disclosure is to provide a method forsignalling information about a number of antenna ports a transmit nodecomprises. Another object of the disclosure is to provide a method whichsolves the problem of backwards compatibility described above. Yetanother object of the disclosure is to provide a solution to the aboveproblem which is simple and easy to implement in a wirelesscommunication system.

According to an aspect of the disclosure the aforementioned objects areachieved by a method in a wireless communication system for signallingnumber of antenna ports which a transmit node comprises. According tothe method a communication signal is transmitted carrying information onnumber of at least one antenna port of the transmit node, wherein theinformation on the number of at least one antenna port is partitionedand provided distributed over at least two predefined parts of thecommunication signal.

According to another aspect of the disclosure the aforementioned objectsare achieved by a method in a transmit node in a wireless communicationsystem for signalling number of antenna ports which the transmit nodecomprises. According to the method, the transmit node transmits acommunication signal carrying information on number of at least oneantenna port of the transmit node, wherein the information on the numberof at least one antenna port is partitioned and provided distributedover at least two predefined parts of the communication signal.

According to an embodiment of the above-mentioned aspect of thedisclosure, the wireless communication system is a LTE-A communicationsystem and the transmit node is a base station or a relay station.

According to yet another aspect of the disclosure the aforementionedobjects are achieved by a method in a receive node in a wirelesscommunication system for receiving signals indicating number of antennaports which a transmit node comprises. According to the method, thereceive node receives a communication signal carrying information onnumber of at least one antenna port of the transmit node, wherein theinformation on the number of at least one antenna port is partitionedand provided distributed over at least two predefined parts of thecommunication signal.

According to an embodiment of the above-mentioned aspect of thedisclosure, the wireless communication system is a LTE-A communicationsystem and the receive node is a mobile station such as a UE.

According to yet another aspect of the disclosure the aforementionedobjects are achieved by a transmit node for signalling number of antennaports which the transmit node comprises. The transmit node is arrangedto provide and transmit a communication signal in the wirelesscommunication system carrying information on number of at least oneantenna port of the transmit node, wherein the information on the numberof at least one antenna port is partitioned and provided distributedover at least two predefined parts of the communication signal.

According to yet another aspect of the disclosure the aforementionedobjects are achieved by a receive node for receiving signals indicatingnumber of antenna ports which a transmit node comprises. The receivenode is arranged to receive and process a communication signal carryinginformation on number of at least one antenna port of the transmit node,wherein the information on the number of at least one antenna port ispartitioned and provided distributed over at least two predefined partsof the communication signal.

The transmit node and the receive node may further be configured inaccordance with the different embodiments of the methods above.

The present disclosure provides an alternative method for signalling anumber of antenna ports which a transmit node comprises. The disclosurealso makes it possible for LTE-A UEs to obtain information about theantenna port configuration for a transmit node (e.g. a eNB or a relaynode) for performing communication with the same, and at the same timeinformation for LTE-A UEs is transparent to LTE UEs and has no impact onthe LTE UEs. Therefore, a solution to the backwards compatibilityproblem described above is also provided by the disclosure.

Other advantages and applications of the present disclosure will beapparent from the following detailed description of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The appended drawings are intended to clarify and explain the presentdisclosure in which:

FIG. 1 shows the procedure of blind detection of PBCH in LTE;

FIG. 2 shows the procedure of blind detection of PBCH in LTE Advanced(LTE-A);

FIG. 3 shows a principal structure of an exemplary transmittingapparatus according to the disclosure; and

FIG. 4 shows a principal structure of an exemplary receiving apparatusaccording to the disclosure.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present disclosure relates to a method in a wireless communicationfor signalling information about a number of antenna ports a transmitnode comprises, where the transmit node can be a base station, eNB,relay station or a relay node. According to an embodiment of the presentdisclosure information about the number of deployed DL antenna ports inLTE-A system is classified into type I and type II information. Type Iinformation indicates the number of LTE antenna ports, and type IIinformation indicates the number of antenna ports defined by LTE-ACSI-RS, or also indicates the total number of antenna ports which aredefined by both LTE CRSs and LTE-A CSI-RSs.

Thus, type I and type II information will indicate information about anumber of different types of antenna ports. In the LTE-A system, LTE UEsonly need to receive type I information to know the exact number of LTEantenna ports, and then use the obtained antenna port information toperform communication with a LTE-A eNB; while LTE-A UEs will receiveboth type I and type II information for different purposes, i.e. thetype I information is used for demodulating one or more controlchannels, and the type II information is used for channel measurement tosupport high layer transmission.

Therefore, a method in a wireless communication system for signalling anumber of antenna ports which a transmit node comprises is presented.According to the method, a communication signal is transmitted carryinginformation about a number of at least one antenna port of the transmitnode. The information about the number of at least one antenna port ispartitioned and provided distributed over at least two predefined partsof the communication signal.

The communication signal is according to the disclosure a number of bitstransmitted on at least one physical channel, and the information aboutthe number of antenna port is partitioned into at least two parts, whichare distributed in different parts among the number of bits of thecommunication signal. In this manner, the antenna port information isembedded into the communication signal, i.e. the communication signalcarries the antenna port information. At least one part of thecommunication signal should be identified by LTE UEs, and at least oneanother part of the communication signal should be transparent to LTEUEs, which in one embodiment of the disclosure corresponds to a firstand second predetermine part of the communication signal, respectively.

To support backwards compatibility and achieve transparent operation ofLTE UEs in LTE-A cells, type I information corresponding to the firstpartitioned part of the information about the number of antenna portscan in another embodiment of the disclosure be conveyed using the sameprinciple as in LTE cells, and it is detectable both to LTE and LTE-AUEs. Thus, type I information is implicitly transmitted throughscrambling the CRC bits of a Broadcast Channel (BCH) transport blocktransmitted on a PBCH with a CRC mask sequence corresponding to type Iinformation, and the PBCH will be transmitted using at most four LTEantenna ports, wherein the BCH transport block, including the scrambledCRC bits, corresponds to the communication signal, and the scrambled CRCbits correspond to the first predefined part of the communicationsignal. The question regarding how many antenna ports that are used fortransmitting the PBCH depends on the configuration of LTE antenna portsin a LTE-A cell.

After detecting type I information, the LTE UE will continue operationaccording to the identified number (one, two or three) of antenna portsin that cell. However, an LTE-A UE also has to decode type IIinformation corresponding to the second partitioned part of theinformation about the number of antenna ports before it can obtain theexact information about the number of deployed antenna ports the LTE-AUE may use, since a LTE-A UE has to find out the number of antenna portsdefined by LTE-A CSI-RSs for channel measurement. Therefore, the type IIinformation is detectable only to LTE-A UEs.

In the LTE Rel-8 system, the size of a BCH transport block transmittedon a PBCH is 24 bits, and there are 10 spare bits which are reserved forfuture communication system. The 10 spare bits are set to zero, and LTEUEs will ignore the 10 spare bits to guarantee backwards/forwardcompatibility, i.e. LTE UEs will not interpret the 10 spare bitsregardless of what kind of information that is embedded into the 10spare bits. Thus, one or more of the 10 spare bits or states representedby the 10 bits can be used to indicate type II information, and therewill not be any impact on LTE UEs PBCH detection and the interpretationof the information bits on the BCH, wherein the one or more of the 10spare bits in BCH transport block correspond to the second predefinedpart of the communication signal. Regarding how many bits or states thatare needed for indicating the number of antenna ports defined by LTE-ACSI-RS depends on the definition of LTE-A CSI-RS. After LTE-A UEssuccessfully detect the PBCH, i.e. the CRC detection is correct, type Iinformation will be obtained, and then the LTE-A UEs further detect thecontent of the BCH transport block transmitted on the PBCH to obtain thetype II information. In other words, if the PBCH is correctly detectedby LTE-A UEs they will know the exact number of antenna ports. In thisway, LTE UEs and LTE-A UEs can obtain their desired antenna portinformation, respectively, and this signalling method has no impact onLTE UE performance, and therefore transparent to LTE UEs, i.e. therequirement of backwards compatibility is achieved.

In the following further embodiments of the disclosure in terms ofdefinition of LTE-A CSI-RSs and the relation between LTE CRSs and LTE-ACSI-RSs are disclosed.

Embodiment A

When the maximum number of supported layers by a LTE-A eNB (or basestation) to LTE-A UEs is eight, the number of LTE-A antenna ports willbe eight. The eight LTE-A antenna ports are defined by eight LTE-ACSI-RSs for either channel measurement, or for both channel measurementand demodulation to support eight layers transmission. Furthermore, theeight LTE-A CSI-RSs are independent of LTE CRSs, and the number of LTEantenna ports defined by LTE CRSs can be configurable.

The number of configured LTE antenna ports in a LTE-A cell can be one,two or four based on the actual situation of the system. For instance,there may be more LTE UEs to be supported at the beginning stage of aLTE-A system, and hence e.g. four LTE antenna ports can be configured tosupport LTE UEs; as evolution of system or time passing, there may bemore and more LTE-A UEs in the system instead of LTE UEs, so it may notbe necessary to configure four LTE antenna ports in this situation forreducing RS overhead.

In the case when a LTE-A eNB supports up to four layers transmission forLTE-A UEs, the number of LTE-A antenna ports will be four and the numberof LTE antenna ports is four. In this case, no new LTE-A CSI-RSs aredefined and LTE-A UEs will use the four LTE antenna ports to performboth channel measurement and demodulation.

If the maximum supported layers for LTE-A UEs by a LTE-A eNB is one ortwo, there is similar antenna port configuration as in the case for upto four layers transmission, i.e. there is no new LTE-A CSI-RSs inaddition to LTE antenna ports. The antenna port configuration in thisembodiment is summarized in Table 1.

TABLE 1 Antenna port configuration in LTE-A Maximum of layers Number ofLTE antenna Number of antenna supported for LTE-A ports defined by portsdefined by UEs by a LTE-A eNB LTE CRS LTE-A CSI-RS 1 1 0 2 2 0 4 4 0 8 18 8 2 8 8 4 8

Based on Table 1, one bit or two states can be used to indicate type IIinformation, i.e. the number of antenna ports defined by LTE-A CSI RSsis zero or eight. For example, the type II is one bit information, where‘0’ could indicate that there is no LTE-A CSI-RS in the LTE-A cell, andLTE-A UEs should use the LTE antenna ports for channel measurement anddemodulation, and ‘1’ could indicate that there are eight LTE-A CSI-RSsin addition to a number of LTE CRSs indicated by type I information.

TABLE 1.1 Encoding type II information Type II Number of antenna portsinformation defined by LTE-A CSI-RS ‘1’ 8 ‘0’ 0

Embodiment B

When the maximum number of supported layers for LTE-A UEs by LTE-A eNBis one, two or four, the antenna port configuration is the same as inembodiment 1 above. If the maximum supported layers by LTE-A eNB iseight, the number of LTE antenna ports is assumed to be n, where n=1, 2,or 4, and the new added LTE-A CSI-RSs is 8−n. LTE-A UEs use thecombination of LTE CRSs and LTE-A CSI-RSs to do channel measurement,i.e. 8−n number of CSI-RSs and n number of LTE CRSs. The possibleantenna port configurations are summarized in Table 2.

TABLE 2 Antenna port configurations in LTE-A Maximum Number of of layersLTE Number of supported antenna ports antenna ports for LTE-A UEsdefined by defined by by a LTE-A eNB LTE CRS LTE-A CSI-RS 1 1 0 2 2 0 44 0 8 1 7 8 2 6 8 4 4

In this embodiment there are two possible solutions to indicate thenumber of LTE-A antenna ports. Alternative 1: two bits or four statesare needed to represent type II information. For example, type IIinformation indicated by two bits: ‘00’, ‘01’, ‘10’ and ‘11’ representthat the number of LTE-A CSI-RSs is 0, 4, 6 and 7, respectively, whichis shown in Table 2.1.

TABLE 2.1 Encoding type II information bits Type II information Numberof antenna ports defined by LTE-A CSI-RS ‘00’ 0 ‘01’ 4 ‘10’ 6 ‘11’ 7

Alternative 2: only one bit is used to indicate type II information.Given that the number of LTE antenna ports n is detected, the number ofLTE-A antenna ports has only two possible values, i.e. 0 and 831 n,which can be indicated by one bit as shown in Table 2.2 below.

TABLE 2.2 Encoding type II information bits Type II information Numberof antenna ports defined by LTE-A CSI-RS ‘1’ 8-n ‘0’ 0

Embodiment C

Assuming the maximum number of supported layers for LTE-A UEs at a LTE-AeNB is N and the number of configured LTE antenna ports is M, whereM<=N, and M=1, 2, or 4. When M<N, the number of LTE-A CSI-RS will be N,otherwise it will be zero. This type of antenna port configuration isillustrated in Table 3.

TABLE 3 Antenna port configurations in LTE-A Maximum of Number of layersfor LTE Number of LTE-A UEs antenna ports antenna ports supported bydefined by defined by a LTE-A eNB LTE CRS LTE-A CSI-RS 1 1 0 2 1 2 2 0 41 4 2 4 4 0 8 1 8 8 2 8 8 4 8

If the number of antenna ports defined by LTE-CSI RSs is zero, it meansthat LTE-A UEs will use LTE antenna ports to measure the channel forsupporting multiple layers transmission. The type II information can beencoded with two bits as shown in Table 3.1 below.

TABLE 3.1 Encoding type II information bits Number of antenna ports TypeII defined by LTE-A CSI-RS information Case 1 Case 2 Case 3 ‘00’ 0 0 0‘01’ 2 x x ‘10’ 4 4 x ‘11’ 8 8 8

The three cases represent that the number of LTE antenna ports is one,two and four, respectively. The symbol ‘x’ in Table 3.1 indicates aninvalid state.

Embodiment D

Following the assumption in the embodiment above, if M<N, the number ofLTE-A CSI-RSs will be N−M, otherwise it will be zero.

TABLE 4 Antenna port configurations in LTE-A Maximum of Number of layersfor LTE Number of LTE-A UEs antenna ports antenna ports supported bydefined by defined by a LTE-A eNB LTE CRS LTE-A CSI-RS 1 1 0 2 1 1 2 0 41 3 2 2 4 0 8 1 7 8 2 6 8 4 4

When the maximum supported layers for LTE-A UEs by LTE-A eNB is equal tothe number of LTE antenna ports, no LTE-A CSI will be defined and LTE-AUEs will use LTE antenna ports for channel measurement and demodulation.Otherwise, a number of additional LTE-A CSIs is defined and thecombination of LTE CRSs and LTE-A CSIs is used by LTE-A UEs for channelmeasurement. In this case, LTE-A antenna ports include both LTE antennaports and antenna ports defined by LTE-A CSI. The type II informationcan be encoded as shown in Table 4.1.

TABLE 4.1 Encoding type II information bits Number of antenna ports TypeII defined by LTE-A CSI-RS information Case 1 Case 2 Case 3 ‘00’ 0 0 0‘01’ 1 2 4 ‘10’ 3 6 x ‘11’ 7 x x

It should be noted that the interpretation of the type II information isdifferent in different cases, i.e. the number of configured LTE antennaports. LTE-A UEs will interpret the type II information depending on thedetected type I information.

Embodiment E

In this embodiment, the only difference from the above embodiment isthat eight LTE-A CSIs are defined when the maximum of layers supportedby LTE-A eNB is eight.

TABLE 5 Antenna port configuration in LTE-A Maximum of Number of layersfor LTE Number of LTE-A UEs antenna ports antenna ports supported bydefined by defined by a LTE-A eNB LTE CRS LTE-A CSI-RS 1 1 0 2 1 1 2 0 41 3 2 2 4 0 8 1 8 8 2 8 8 4 8

The type II information can in this embodiment be encoded with two bitsof information or four states. In this embodiment, we assume that fourstates of the 10 sparse PBCH bits are used to represent the type IIinformation.

TABLE 5.1 Encoding of type II information bits Number of antenna portsType II defined by LTE-A CSI-RS information Case 1 Case 2 Case 3‘0000000001’ 0 0 0 ‘0000000010’ 1 2 x ‘0000000011’ 3 x x ‘0000000100’ 88 8

Embodiment F

In order to support LTE-A UEs multiple layers transmission, a number ofLTE-A CSI are defined, which is equal to the maximum supported layers byLTE-A eNB in this case. There are two embodiments following thisprinciple,

-   -   The number of LTE antenna ports is configurable only when there        are eight LTE-A CSI.    -   The number of LTE antenna ports is configurable for any number        of LTE-A CSI.

Embodiment F1

One bit type II information can be used to indicate the antenna portconfiguration shown in Table 6.1.

TABLE 6.1 The number of LTE antenna ports is only configurable whenthere are eight LTE-A CSI-RSs Maximum of Number of layers for LTE Numberof LTE-A UEs antenna ports antenna ports supported by defined by definedby a LTE-A eNB LTE CRS LTE-A CSI-RS 1 1 1 2 2 2 4 4 4 8 1 8 8 2 8 8 4 8

TABLE 6.1.1 Encoding type II information bits Number of antenna portsType II defined by LTE-A CSI-RS information Case 1 Case 2 Case 3 ‘0’ 1 24 ‘1’ 8 8 8

Embodiment F2

TABLE 6.2 The number of LTE antenna ports is configurable Maximum ofNumber of layers for LTE Number of LTE-A UEs antenna ports antenna portssupported by defined by defined by a LTE-A eNB LTE CRS LTE-A CSI-RS 1 11 2 1 2 2 2 4 1 4 2 4 4 4 8 1 8 8 2 8 8 4 8

In this embodiment of the disclosure, the type II information is encodedas two bits.

TABLE 6.2.1 Encoding type II information bits Number of antenna portsType II defined by LTE-A CSI-RS information Case 1 Case 2 Case 3 ‘00’ 1x x ‘01’ 2 2 x ‘10’ 4 4 4 ‘11’ 8 8 8

Embodiment G

When the maximum of layers for LTE-A UEs supported by LTE-A eNB is one(or two), there will be one (or two) LTE antenna ports which are usedfor LTE-A channel measurement and demodulation, and no new LTE CSI-RSsare defined; the number of LTE antenna ports is configurable and somenew LTE-A CSI-RSs are defined shown in Table below.

TABLE 7 Antenna port configuration in LTE-A Maximum of Number of layersfor LTE Number of LTE-A UEs antenna ports antenna ports supported bydefined by defined by a LTE-A eNB LTE CRS LTE-A CSI-RS 1 1 0 2 2 0 4 1 42 4 4 0 8 1 8 8 2 8 8 4 8

In this case, three states are sufficient to represent type IIinformation as shown in Table 7.1.

TABLE 7.1 Encoding type II information bits Type II information Numberof antenna ports defined by LTE-A CSI-RS ‘0000000001’ 0 ‘0000000010’ 4‘0000000011’ 8

An example of how transmission of information about a number of antennaports that a transmit node comprises may be implemented in a LTE-Acommunication system is described below, in which the antenna portconfiguration information is transmitted through a LTE-A PBCH. The blinddetection of LTE-A PBCH is illustrated in FIG. 2.

The transmitting procedure of a LTE-A PBCH involves the steps of:

-   -   Using the entire transport block of LTE-A PBCH a₀, a₁, . . .        a_(A-1) (in which one or more explicit bits corresponding to        type II information indicate the number of antenna ports defined        by LTE-A CSI-RS) to calculate the CRC parity bits p₀, p₁, . . .        p_(L-1), where A and L are the value of transport block size and        CRC bits size, respectively.    -   Scrambling the calculated CRC parity bits p₀, p₁, . . . p_(L-1)        with a CRC mask x₀ ⁴, x₀ ⁴, . . . x₁₅ ⁴ corresponding to type I        information about the number of LTE antenna ports, i.e.        c_(i)=(p_(i)+x_(i) ⁴)mod 2, i=0, 1, . . . , 15.    -   Attaching the scrambled CRC c₀, c₁, . . . c₁₅ to the transport        block of LTE-A PBCH a₀, a₁, . . . a_(A-1) for obtaining a₀, a₁,        . . . a_(A-1), c₀, c₁, . . . , c₁₅.    -   Performing channel coding, rate matching, and modulation on the        information bits a₀, a₁, . . . a_(A-1), c₀, c₁, . . . , c₁₅.    -   Performing spatial encoding on the modulation symbols such as        SFBC or SFBC+FSTD depending on the number of LTE antenna ports.    -   Mapping the output of the above step onto the reserved resources        for PBCH on a number of LTE antenna ports.

According to yet another embodiment of the disclosure, in addition totransmit the type II information in the BCH transport block, the type IIinformation can also be transmitted on other channels, such as PhysicalDownlink Shared Channel (PDSCH). Dynamic Broadcast Channel (DBCH) isanother type of broadcast transport channel which is mapped onto thePDSCH on the physical layer. This type of PDSCH is transmitted in apredefined sub-frame, and all active UEs in a cell will receive thistype of PDSCH to obtain further system information in addition tobroadcast information conveyed on the PBCH. In a LTE-A system, some newinformation bits can be defined in DBCH, which are only valid for LTE-AUEs, e.g. several bits in DBCH are used to indicate the number ofantenna ports defined by LTE-A CSI-RS. In this case, the communicationsignal corresponds to a BCH transport block including scrambled CRC bitsand DBCH transport block mapped onto PDSCH together, and the first andsecond predefined parts of the communication signal correspond toscrambled CRC bits of the BCH and the information bits of the DBCHtransport block, respectively.

Before a LTE-A UE obtains the number of LTE-A antenna ports, it can onlyknow the number of LTE antenna ports through detecting PBCH. In order todetect the PDSCH on which DBCH containing type II information is mapped,this PDSCH must be transmitted on the configured LTE antenna ports whichare indicated by type I information, otherwise LTE-A UE cannot detectthe PDSCH. Thus, the procedure is that a LTE-A UE firstly detects thePBCH to get the number of LTE antenna ports, and then go to thepredefined sub-frame to detect the special PDSCH carrying DBCHinformation. After the detection of the PDSCH, the LTE-A UE will obtainthe number of LTE-A antenna ports, and then can switch to LTE-A mode.

The present disclosure also relates to a transmitting apparatus and areceiving apparatus configured according to the different embodiments ofthe method above.

FIG. 3 shows a principle structure of an exemplary transmittingapparatus (601) for a wireless communications system according to thepresent disclosure. The transmitting apparatus comprises transmissioncircuitry (TX, 606) having one or more antenna ports for transmission ofcommunication signals over one or more antennas (602-605). Prior totransmission, signals carrying information on a number of antenna portsare processed in a processing circuitry (μ, 607). Different signal partsare predefined preferably in memory devices of the transmittingapparatus (601) included in or connected to the processing circuitry(607). The processing circuitry comprises modules for partitioning theinformation on a total number of antenna port(s) and distributing thepartitioned information to be provided in two or more predefined partsof a transmitted communication signal, the predefined parts preferablybeing stored in memory circuitry. According to an embodiment of thedisclosure, the transmitting apparatus is preferably a base station(eNB) or a relay node.

FIG. 4 shows a principle structure of an exemplary receiving apparatus(701) for a wireless communications system according to the presentdisclosure. The receiving apparatus comprises a receiving circuitry (RX,704) connected to one or more antennas (702, 703). The receivingcircuitry comprises electronics for reception of a communication signal.The receiving apparatus (701) comprises a processing circuitry (μ, 705)operating on received signals provided via the receiving circuitry(704). The processing circuitry comprises modules for determining fromtwo or more predefined parts of a received communication signaltransmitted from e.g. a base station, the predefined parts preferablybeing stored in memory circuitry of the receiving apparatus. Theelectronics of the processing circuitry determine from at least a secondpart of the communication signal a total number of transmission antennaports to be applied. As need be, also the predefined first part of thecommunication signal is processed for determining the number of antennaports to be applied for subsequent signal processing. According to anembodiment of the disclosure, the receiving apparatus is preferably amobile station, such as a UE.

Furthermore, as understood by the person skilled in the art, the methodfor signalling number of antenna ports according to the presentdisclosure may be implemented in a computer program, having code means,which when run in a computer causes the computer to execute the steps ofthe method. The computer program is included in a computer readablemedium of a computer program product. The computer readable medium mayconsist of essentially any memory, such as a ROM (Read-Only Memory), aPROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), a Flashmemory, an EEPROM (Electrically Erasable PROM), or a hard disk drive.

It should also be understood that the present disclosure is not limitedto the embodiments described above, but also relates to and incorporatesall embodiments within the scope of the appended independent claims.

What is claimed is:
 1. A method of signaling a quantity of antenna portsof a transmitting apparatus in a wireless communication system, themethod comprising: transmitting, by the transmitting apparatus, a firsttype information on a physical broadcast channel (PBCH), wherein thefirst type information indicates a first number of an antenna port ofthe transmitting apparatus corresponding to a cell-specific referencesignal (CRS); and transmitting, by the transmitting apparatus, a secondtype information on a physical downlink shared channel (PDSCH), whereinthe second type information indicates a second number of an antenna portof the transmitting apparatus corresponding to a channel stateinformation reference signal (CSI-RS), wherein the PDSCH is transmittedon an antenna port indicated by the first type information.
 2. Themethod of claim 1, wherein the first type information is detectable toboth a long term evolution user equipment (LTE UE) and a long termevolution-advanced user equipment (LTE-A UE).
 3. The method of claim 2,wherein the second type information is only detectable to the LTE-A UE.4. The method of claim 1, wherein the first type information indicatesthe first number of the antenna port of the transmitting apparatuscorresponding to the CRS being one, two, or four.
 5. The method of claim1, wherein the second type information indicates the second number ofthe antenna port of the transmitting apparatus corresponding to theCSI-RS being zero, two, four, or eight.
 6. The method of claim 1,wherein the first type information is used for demodulating a controlchannel.
 7. The method of claim 1, wherein the second type informationis used for channel measurement.
 8. The method of claim 1, wherein thetransmitting apparatus supports more than four layers transmission. 9.The method of claim 1, wherein the transmitting apparatus is a basestation.
 10. A transmitting apparatus, comprising at least one processorconfigured to: transmit a first type information on a physical broadcastchannel (PBCH), wherein the first type information indicates a firstnumber of an antenna port of the transmitting apparatus corresponding toa cell-specific reference signal (CRS); and transmit the second typeinformation on a physical downlink shared channel (PDSCH), wherein thesecond type information indicates a second number of an antenna port ofthe transmitting apparatus corresponding to a channel state informationreference signal (CSI-RS), the PDSCH configured to be transmitted on anantenna port indicated by the first type information.
 11. Thetransmitting apparatus of claim 10, wherein the first type informationis detectable to both a long term evolution user equipment (LTE UE) anda long term evolution-advanced user equipment (LTE-A UE).
 12. Thetransmitting apparatus of claim 11, wherein the second type informationis only detectable to the LTE-A UE.
 13. The transmitting apparatus ofclaim 10, wherein the first type information indicates the first numberof the antenna port of the transmitting apparatus corresponding to theCRS being one, two, or four.
 14. The transmitting apparatus of claim 10,wherein the second type information indicates the second number of theantenna port of the transmitting apparatus corresponding to the CSI-RSbeing zero, two, four, or eight.
 15. The transmitting apparatus of claim10, wherein the first type information is configured to be used fordemodulating a control channel.
 16. The transmitting apparatus of claim10, wherein the second type information is configured to be used forchannel measurement.
 17. The transmitting apparatus of claim 10, whereinthe transmitting apparatus supports more than four layers transmission.18. The transmitting apparatus of claim 10, wherein the transmittingapparatus is a base station.
 19. A wireless communication system,comprising a transmitting apparatus and a receiving apparatus, whereinthe transmitting apparatus comprises at least one processor configuredto: transmit a first type information to the receiving apparatus on aphysical broadcast channel (PBCH), wherein the first type informationindicates a first number an antenna port of the transmitting apparatuscorresponding to a cell-specific reference signal (CRS); and transmit asecond type information to the receiving apparatus on a physicaldownlink shared channel (PDSCH), wherein the second type informationindicates a second number of an antenna port of the transmittingapparatus corresponding to a channel state information reference signal(CSI-RS), the PDSCH being transmitted on an antenna port indicated bythe first type information.
 20. The system of claim 19, wherein thefirst type information indicates the first number of the antenna port ofthe transmitting apparatus corresponding to the CRS being one, two, orfour.
 21. The system of claim 20, wherein the second type informationindicates the second number of the antenna port of the transmittingapparatus corresponding to the CSI-RS being zero, two, four, or eight.